Order values within column according to values within different column by group in R

Question

I have the following panel data set:

group  i  f  r  d
1      4  8  3  3
1      9  4  5  1
1      2  2  2  2
2      5  5  3  2
2      3  9  3  3
2      9  1  3  1

I want to reorder column i in this data frame according to values in column d for each group. So the highest value for group 1 in column i should correspond to the highest value in column d. In the end my data.frame should look like this:

group  i  f  r  d
1      9  8  3  3
1      2  4  5  1
1      4  2  2  2
2      5  5  3  2
2      9  9  3  3
2      3  1  3  1

Answer 1

original (wrong)

You can achieve this using dplyr and rank:

library(dplyr)

df1 %>% group_by(group) %>%
  mutate(i = i[rev(rank(d))])

Edit

This question is actually trickier than it first seems and the original answer I posted is incorrect. The correct solution orders by i before subsetting by the rank of d. This gives OP's desired output which my previous answer did not (not paying attention!)

df1 %>% group_by(group) %>%
  mutate(i = i[order(i)][rank(d)])

# A tibble: 6 x 5
# Groups:   group [2]
#  group     i     f     r     d
#  <int> <int> <int> <int> <int>
#1     1     9     8     3     3
#2     1     2     4     5     1
#3     1     4     2     2     2
#4     2     5     5     3     2
#5     2     9     9     3     3
#6     2     3     1     3     1